Fabrication of a structural member or workpiece (such as, for example, a structural steel I-beam, wide flange H-beam, angle channel, flat plate, etc.) may require processing such as cutting, drilling, punching, and shearing portions of the workpiece. Conventional and specialized processing machines perform these processing operations. For example, a processing machine can be used to drill holes in a workpiece.
In one type of processing line or layout, one or more workpieces are supported lengthwise on a series of storage tables or transfer stands that are located adjacent to a conveyor. The conveyor leads to, and away from, one or more processing machines. The conveyor is typically an elevated structure having chain-driven rollers that define a conveying path and that are capable of supporting and conveying the workpiece along the conveying path. Each transfer stand is typically many times longer than its width. A plurality of such transfer stands are typically arranged in a spaced-apart, parallel relationship with each transfer stand oriented perpendicular to the conveying path. The transfer stands together support the workpiece lying across them while the workpiece waits to be transferred: (i) onto the conveyor for processing; or (ii) elsewhere subsequent to processing (e.g., such as being lifted off of the transfer stands by a forklift). Each of the transfer stands is typically an elevated structure with support surfaces that define a transfer path and that are capable of supporting one or more workpieces.
Some prior art transfer stands include a chain-driven carriage that is movable with respect to a support surface of the transfer stand, and the carriage further has a hydraulic lift. The carriage (i) travels underneath the workpiece, (ii) raises upwards through hydraulic actuation to lift the entire workpiece from the support surface of the transfer stand, (iii) moves the workpiece generally along the transfer path defined by the transfer stand, and then (iv) lowers the workpiece onto the rollers of the conveyor. This process may be reversed if the workpiece is being moved from the conveyor onto a transfer stand.
This process may be manually performed by an operator of the transfer stand, or it may be automated through the use of sensors and programmable logic controllers. For heavy workpieces such as wide flange, structural H-beams, the hydraulic lift-type carriage may require a large amount of force from the hydraulic lift, which must fully lift the workpiece in order to transfer the workpiece onto or off of the transfer stand. Furthermore, providing the carriage with a hydraulic lift may add to the complexity and manufacturing cost of the transfer stand.
Another type of prior art transfer stand contains a chain-driven, dragging carriage that is movable with respect to a support surface of the transfer stand. The carriage has a movable push member or “dog” that has a retracted position for allowing the carriage to travel past the workpiece, and the dog has a moved position for contacting a portion of the workpiece (e.g., such as a flange of the workpiece) to move the workpiece by pushing, pulling, or dragging the workpiece along a support surface of the transfer stand to the rollers of the conveyor, or vice versa. This process may also be manually performed by an operator of the transfer stand, or the process may be automated through the use of sensors and programmable logic controllers. For relatively heavy workpieces, however, the dragging-type carriage may also require a large amount of force from the chain drive due to the friction force created by the workpiece resting on the support surface of the transfer stand. Furthermore, dragging such a heavy workpiece in this manner may cause increased wear of the transfer table support surface, the conveyor rollers, and/or the chain drive of the dragging-type transfer table.
It would be desirable to provide an improved apparatus or transfer table for transferring a workpiece wherein the above-discussed problems of the prior art transfer tables could be eliminated, or at least substantially minimized.
It would be especially desirable for such an improved transfer table to reduce the forces required to move a workpiece, reduce wear on the transfer table, conveyor, and/or workpiece, and further eliminate the need for a complicated hydraulic carriage for lifting the workpiece.
It would further be desirable if such an improved transfer table could be readily operated by an appropriate control system, could accommodate a variety of different types of workpieces (e.g., flat plates, channels, angles, beams, etc.), could produce accurate and repeatable transfer of workpieces, and could relatively easily accommodate changes in the types and sizes of the workpieces being transferred.
It would also be beneficial if such an improved transfer table could cooperate with, and fit into, an existing processing line or layout.
Further, it would be beneficial if such an improved transfer table could be manufactured, installed, and operated without incurring excessive costs or expenses.